Work through flow and see what is needed

event handlers

input values

adding values to data structure

adding new value to UI

calculations

updating UI

Structuring with Modules

help with organization

help with keeping data private or public

can break in to UI module and data module and controller module

UI module: input values add new item to UI update UI

Data module: new item to data structure calculations

Controller module: event handler

Module pattern:

Laying out separate modules

Separation of concerns - each part of code only worries with it's job